Wheel bearing device with rotation detector

A rotation detector equipped wheel support bearing assembly for rotatably supporting a vehicle wheel relative to a vehicle body structure, which assembly comprises:

• an outer member that serves as a stationary member and having an inner periphery rolling surfaces;
• an inner member that serves as a rotating member having an outer periphery formed with rolling surfaces opposed to the respective rolling surfaces in the outer member;
• a plurality of rolling elements interposed between those opposed rolling surfaces;
• a magnetic encoder fitted to the outer peripheral surface of the inner member at a location adjacent one end thereof;
• an annular sensor holder made of a resin and fitted to the outer member through a core metal provided in the outer periphery, the annular sensor holder having a magnetic sensor built therein and confronting the magnetic encoder with an axial gap intervening therebetween;
• and
• a sealing unit arranged at an outer position axially outwardly, relative to the bearing assembly, of the magnetic encoder and the magnetic sensor for sealing a space delimited between the sensor holder and the inner member;
• wherein the magnetic encoder is in the form of a plastic magnetic encoder that includes a magnet defining a to-be-detected portion is in the form of a plastic magnet, and
• wherein the sealing unit includes a first sealing plate mounted on an outer peripheral surface of the inner member, a second sealing plate mounted on an inner peripheral surface of the sensor holder and a sealing member made of an elastic material.